The aim of the research program of which this application is a part is to understand the role of the cerebral cortex in motor function. An understanding of the functions and dysfunctions of the cerebral cortex is contingent upon revealing physiological and structural aspects of cortical circuitry. The proposed studies will address one of the least understood aspects of cortical circuitry, that of intrinsic, or intracortical synaptic relationships. By combining electrophysiological and anatomical techniques, data on intrinsic relationships in the motor cortex of the cat. One line of investigations will examine intrinsic connections within and among identified functional columns in the motor cortex. A functional column in the motor cortex is comprised of a group of cells that are responsible for the activity of a single muscle, or a small group of related muscles. By deciphering the patterns of connections among cells responsible for the same muscle, and between groups of cells responsible for different muscles, we will gain an insight into the mechanisms by which the motor cortex activates different sets of muscles to produce voluntary movements. In addition, intracortical synaptic relationships formed by individual pyramidal tract cells will be revealed, using intracellular recording and labeling techniques. Pyramidal tract cells are involved in the output stage of information processing in the motor cortex, and convey this output directly to the spinal cord. The intrinsic interactions between pyramidal tract neurons are important for controlling and coordinating the contractions of specific groups of muscles. The patterns of intracortical synaptic relationships these cells form within a single functional column, and between different functional columns will then be examined. Electron microscopical, immunocytochemical, and histochemical techniques will be employed to study the types and numbers of intracortical synapses these cells form, and to reveal the identity of neurons postsynaptic to these cells. These studies will provide data necessary for the elucidation of the mechanisms of motor cortical function, namely the execution of voluntary movements, and ultimately will advance our understanding of motor dysfunctions.